Schickard’s Calculator and The Pascaline

Schickard built two calculators around 1623. One, for his astronomer friend Johannes Kepler, was destroyed by fire. The other is, as far as we know, lost. We know about them only from Schickard’s handwritten letters, which contain sketches of what he had built.

Schickards's Calculator

A 1623 letter from William Schickard to astronomer Johannes Kepler is the only surviving record of Schickard’s calculator.

Schickard combined Napier’s Bones, for multiplication and division, with a toothed-wheel system to add and subtract. It is the earliest known mechanical four-function calculator.

The Pascaline was operated by inserting a stylus at, say, the number “3” position in a toothed wheel, then rotating the wheel until it hit a stop. The complicated and unreliable internal carry mechanism used falling weights instead of linked gears.